Electrostatic atomization of liquid fuel



Aug, 30, 1966 F. E. LUTHER LECTROSTATIC ATOMIZATION OF LIQUID FUEL 2UhGGtSShEBSt 1 Filed May 19, 1965 FIG. 3

lNVENTOR FLOYD E. LUTHER Mung.

FIG. 2

United States Patent Office 3,269,446 ELECTROSTATH? ATGMHZATHUN F LIQUIDFUEL Floyd E. Luther, Berkeley, Calif., asslgnor to Chevron ResearchCompany, a corporation of Delaware Filed May 19, 1965, Ser. No. 467,801tllaims. (til. 158-4) This application is a continuation-in-part of mycopending application Serial No. 251,977, filed January 16, 1963, nowabandoned.

This invention relates to an atomizing liquid fuel burner and, moreparticularly, to a device for atomizing liquid fuels and the like byelectrostatic atomization.

Fuel atomization at low fuel flow rates has not been widely successfulbecause the extremely small orifices needed to restrict flow at flowrates in the order of onehalf /2) gallon per hour or less are easilyclogged by contaminants, debris and fuel degradation products. This hasbeen an area of diligent experimentation with the result that there havebeen developments of varying degrees of success following widelydivergent theories and concepts of atomization. For example, there hasbeen some work in the use of ultrasonic waves to agitate a liquidsurface to produce atomized droplets from it. Others have concernedthemselves with the application of an external deflecting electric ormagnetic field to charged fuel particles and particularly to liquid fuelwhich has been ionized in a flame.

Electrostatic atomization, wherein the liquid is given an electricalcharge of one polarity and attracted to an opposite electrode has alsobeen the subject of considerable effort, but such efforts have beensuccessful only with liquids of relatively high electrical conductivitybecause of a number of substantial problems to be overcome. Manyliquids, such as heating oil, are of very low conductivity and are,therefore, not particularly suited to electrostatic atomization bypreviously tried methods.

Very substantial voltages are required to impose the charge on liquidsof low conductivity and this disadvantage is particularly apparent whendirect current is used, with a charge of one polarity imposed on theliquid and with the electrode at another polarity. With the liquid underthe constant attractive force of the electrode at opposite polarity,liquid droplets tend to be frequently drawn off from the atomizing headbefore a sufficient atomizing electrical charge is transferred thereto.Consequently the quality of the atomization suffers. More over, theconstant attraction of the electrode draws liquid particles which tendto impinge upon the electrode, thereafter to drip off or be drawn off byground potential without being properly atomized. The present inventionovercomes these difficulties.

With alternating current applied to both the atomizing head and theelectrode, satisfactory atomization has been achieved with liquids ofrelatively high electrical conductivity but when liquids of relativelylow conductivity are used atomization occurs only at voltages just belowthat for corona arcdischarge. Consequently, there is often just a verynarrow voltage range within which an alternating current system of thistype may be operated and, under ordinary circumstances, it is difficultto keep such system functioning without generating a short circuit,promoting ion flow between the atomizing head and the electrode. Thepresent invention overcomes these dilficulties.

It is, therefore, an object of this invention to provide an apparatusfor electrostatic atomization which is capable of producing satisfactoryatomization for liquids of relatively low electrical conductivity atvoltages considerably below that for corona arc-discharge.

It is a further object of this invention to provide an 3,269,446Patented August 30, 1966 apparatus for electrostatic atomization whichovercomes the defects of fuel impingement on the electrodes.

It is a further object of this invention to provide an apparatus forelectrostatic atomization which permits liquids of low conductivity tobuild up a satisfactory charge before being drawn off by the attractingelectrode.

Another object of this invention is to provide a novel electrostaticatomizer for furnace fuel oils.

These and other objects and advantages of this invention will becomeapparent from the specification following when read in conjunction withthe accompanying drawings.

In carrying out this invention there is provided a discharge head whichis connected as an electrode in an electrical circuit and which has asurface upon which a film of the liquid to be atomized is formed. Thesurface is proportioned to provide a suficient time of residence of thefilm thereon, as the liquid is drawn from an edge of the surface, toenable a liquid of relatively low electrical conductivity to acquire anelectrical charge from the discharge head. A second electrode of thecircuit is placed adjacent to the edge of the film-forming surface andoperates, at least part of the time, at an opposite polarity to that ofthe discharge head. When the discharge head and the second electrode areof opposite polarity atomized droplets of the liquid are drawn from thedischarge head toward the second electrode. Preferably means areprovided to prevent the atomized liquid from impinging and accumulatingon the second electrode from which it may be drawn off in an unatomizedform by gravity or by the ground potential, as indicated heretofore.

In a preferred embodiment of this invention there is provided adischarge head of conical configuration which is preferably disposedwith its axis upright and with the conical surface diverging downwardlyto a rather sharp annular edge. Fuel is introduced to the outside of theconical surface to flow naturally down toward the location of thehighest charge concentration at the sharp, annular edge and to acquire acharge by means of a direct current potential supplied to the dischargehead. Disposed below and spaced apart from the discharge head is anannular electrode to which an alternating current potential is supplied.Consequently, the liquid on the atomizing head is in a strong electricalfield of one polarity and the electrode is alternately reversingpolarities. When the liquid acquires an electrical charge of thepolarity of the discharge head, charged droplets are drawn from theannular edge of the head during periods of relative opposite polarity ofthe annular electrode. Each interval between such alternating periodswhen the electrode is at the same polarity as the discharge head affordsan opportunity for an electric charge to build up in the liquid. In aburner employing such an atomizing device, there is preferably provideda suitable blower to mix the air and atomized fuel intimately and asuitable flame stabilization means to isolate the flame from theimmediate atomization zone.

In the drawings:

FIG. 1 is a schematic illustration with wiring diagram of a burner withan electrostatic atomizer embodying features of this invention;

FIG. 2 is an isometric view partially in section of a discharge headforming a part of this invention;

FIG. 3 is a vertical sectional view of the discharge head of FIG. 2;

FIG. 4 is an isometric view partially in section of a modified form ofburner assembly embodying features of this invention;

FIG. 5 is an isometric view partly in section of another modification ofan atomizer made in accordance with this invention, and

FIG. 6 is a diagrammatic illustration of the relative conductivity ofvarious liquids.

Referring now to the drawings with greater particularity, the atomizingsystem of my invention is shown in FIG. 1 and may comprise a furnacechamber 2 which may be divided into an atomizing chamber 4 and acombustion chamber 6. Disposed within the atomizing chamber is a liquiddischarge head 8 comprising a conical discharge surface 10 formed ofelectrically conducting material on the cone 11 and over which a liquidfilm is formed, the liquid being distributed over the conicalfilm-forming discharge by means of a feeder 12 having an annular outletport 14. Burner oil or other suitable liquid fuel is delivered to thefeeder 12 from a source thereof (not shown) by any suitable means suchas the conduit 16. The structure of the liquid discharge head 3 will bedescribed in more detail hereinafter but for the present it suffices tostate that it includes the feeder 12, the conical film-forming surface10, and a relatively sharp annular edge 18 formed on the cone 11 at thebottom of surface 11 and toward which the liquid film flows.

Disposed below the liquid discharge head 8 is an attracting electrode 20which draws oppositely charged oil droplets from the relatively sharpdischarge edge 18 of the conical surface 10 to be propelled downwardly,assisted by a low pressure air blower 22, into the zone at the lower endof the atomizing chamber l where the atomized oil droplets arethoroughly mixed with the swirling air. The fuel-air mixture is thendirected to the combustion chamber 6 wherein it is ignited, as by theigniter 23.

Preferably there is provided some suitable flame stabilizer which servesto isolate the flame from the zone of the atomizer and this may beaccomplished in any suitable manner such as by directing the air-fuelmixture through a venturi 24 which maintains the fiow at a velocitygreater than the burning rate so that flame remains within thecombustion chamber 6.

Although the apparatus of this invention may be applied to theatomization of liquids generally, it is particularly applicable to theatomization of liquids which have a relatively low electricalconductivity, such as the fuel oil which is commonly used in domesticheating furnaces and which is designated as No. 2 heating oil. As willbe observed from the comparison illustrated in FIG. 6, No. 2 heating oilhas a conductivity of approximately 1O mho/cm., which is substantiallycomparable to that of mica. Thus, ordinarily, No. 2 heating oil would beconsidered an effective electrical insulator.

Again referring to FIG. 6, No. 2 heating oil can be treated with anadditive to increase its conductivity to approximately 10 mho/cm.without destroying its utility as a fuel oil, but even such a treatedoil is much less electrically conductive than liquids which might beconsidered to have relatively high electrical conductivity, as sea wateror tap water, which range around 10' mho/cm. conductivity.

It would appear, then, that liquids of relatively low electricalconductivity would not be susceptible to atomization by electrostaticmeans because of the inability of such a liquid to take an electricalcharge of suflicient amount to cause the liquid to be attracted to anoppositely charged electrode with enough force to produce atomization ofit. However, by using the techniques of this invention the atomizationof such a liquid can be accomplished.

The particular means of atomizing a liquid fuel electrostatically is asignificant feature of this invention and includes a source ofalternating current 26 which may be, but is not necessarily, a 110 volt,60 cycle source. If desired, the input voltage :may be controlled at 28and connected to high voltage transformers 30 delivering an out put inthe order of 45 kv. over conductors 32 and 34. A branch 35 of line 34 isconnected to one input terminal of a full-wave rectifier such as theschematically illustrated rectifier 36, the line 32 being connected tothe other input terminal.

The primary windings 131 and 131 of transformer 30 are connected inseries. The secondary windings 132 and 134 also are connected in seriesand have between them a center tap to ground as indicated at 135.

With ground taken as the reference datum, or zero potential, during onehalf cycle of transformer output the conductor 32 will beat a positivepotential relative to ground and the conductor 34 will be at a negativepotential relative to ground as illustrated by the symbols in FIG. 1. Onthe other half of the cycle the polarity of the transformer output willbe reversed.

If the corresponding primaries and secondaries of the transformer areelectrically similar to each other, the difference in potential betweenground and the conductor 32 will be equal to the difference in potentialbetween ground and the conductor 34. Therefore, the difference inpotential between the output terminals of the transformer will be equalto twice the difference in potential between either output terminal andground. When the transformer is operating at the portion of the cycle ofthe A.C. input which causes the conductor 32 to be at a positivepotential relative to ground and the conductor 34 to be at acorresponding negative potential, as indicated by the symbols in FIG. 1,the diode 136 passes the positive potential through conductor 32 to theconductor 38, which is electrically connected to the discharge head 8.The diode 137 blocks a short-circuit current flo-w back to thetransformer.

When the transformer is operating on the next half of the cycle theconductor 34 becomes positive relative to ground and the conductor 32becomes negative relative to ground. The diode 137, which is connectedto the conductcr 34 through the conductor 35, then passes the positivepotential to conductor 38 and the diode 136 blocks the short-circuitreturn current flow. Therefore, the conductor 38 and hence the dischargehead 8 operates continuously at full-wave rectified positive potential.

The conductor 38 may be electrically connected to the discharge head 8by connecting the conductor to some portion of the interconnectedapparatus, such as the delivery conduit 16 which then will beelectrically insulated from the furnace chamber as at 39. With thedischarge head at a continuous positive potential an oil film on it willacquire a positive charge. The charge will be particularly concentratedat the relatively sharp lower edge 18 of the cone 11.

The conductor 34 is directly connected to the electrode ring 20 which iselectrically insulated from the furnace chamber, as at 37. Thus the ring21) has impressed on it the alternating current potential of thecorresponding output terminal of the transformer 30.

The potential difference between the discharge head 8 and the electrodering 20 alternates between the full potential difference of thetransformer output and zero as the ring 21 correspondingly alternatesfrom a negative to a positive potential relative to ground. This may beseen by referring again to FIG. 1. When the conductor 32 is at apositive potential relative to ground and the conductor 34- is at acorresponding negative potential, as indicated by the symbols in FIG. 1,the difference in potential between the discharge head and the ring willbe the same as that between the output terminals of the transformer, andalso will be twice as great as that between either output terminal andground.

When the polarity of the output of the transformer is reversed and theconductor 34 has impressed on it a positive potential relative toground, the discharge head, through conductors 35 and diode 137 willhave impressed on it the same potential relative to ground, both inpolarity and amount, as has the electrode ring 20. Therefore, duringthis half of the cycle there will be no difference in potential betweenthe discharge head and the electrode ring.

It follows from the foregoing that since the liquid at the edge 18 ofconical surface 14) is in a position to acquire a positive charge, andan alternating current po tential is impressed on electrode ring 20,there are cyclic alternate periods during which the electrode ringattracts the positively charged liquid from the edge 18. Between theseintervals there are corresponding alternate intervals during which thereis no attraction between the ring and the discharge head and the film ofoil on the conical surface is enabled to build up a charge. Moreover thevoltage and spacing between the electrodes 11 and can be arranged sothat as the oil droplets drawn from the annular edge 18 approach theelectrode ring 20, the charge of the latter is reversed and droplets arerepelled away from it, thus preventing the droplets of oil fromimpinging upon the electrode ring 20 and accumulating thereon. Duringthis time the current of air from the blower 22 will sweep the atomizeddroplets of oil from the chamber 4 into the combustion chamber 6.

It is not necessary for the above-described operation that the innerwall of the furnace chamber be grounded since the atomization of thefuel oil depends primarily on the difference in potential between thedischarge head 8, particularly the annular edge 18, and the electrodering Ztl. However, it may in some installations be desirable to groundthe furnace chamber and such a ground connection is indicated at 81,FIG. 1. It will be noted by reference to this figure and the abovedescription that the electrode ring 24 will have impressed on it analternating difference in potential relative to ground which will tendto draw off any fuel oil droplets which may accumulate on the ring.

As shown in FIG. 1 the cone 11 is preferably arranged with its axisvertical and with its outer surface it) diverging downwardly so that thesharp edge 18 of maximum charge concentration is located at the bottomto permit the oil film to gravitate thereto naturally. Preferably theelectrode ring 20 which, as stated heretofore, is placed adjacent to theedge of the film-forming surface, is spaced elow and concentric with thelower edge 18 to draw oil droplets uniformly therefrom.

Finally, the oil droplets are agitated and intermixed with air, such asfrom a low pressure blower 22 or the like, and ignited in the combustionchamber 6, some suitable means such as the venturi 24 being provided tostabilize burning so as to prevent invasion of the flame into theatomizing zone 4.

Referring now to FIGS. 2 and 3 there is shown a preferred embodiment ofliquid discharge head 8 which will now be described in detail. It willbe noted that the cone 11 is truncated, as at 40, and a series ofcircumferentially spaced cylindrical sectors 42 extend upwardly from thetruncated portion with flow passages 43 formed between them. The sectorsare preferably relieved by a circum' ferential channel at 44 to providea circumferential distribution of liquid to the annular flow orifice 14.The cone 11 is preferably secured to a holder 4-6 which has an internalconical surface 48 at the lower end thereof complementary to and spacedfrom the conical surface 10 to provide the outlet port 14. Threaded,welded or otherwise secured within the holder 46 is a flow distributor4-9 which is formed with axially disposed distributing conduits 51communicating with the flow passages 43. A bolt member projects from thelower end of the flow distributor 49 and is threaded into the cone tosecure it to the holder 46. Fuel is introduced to the feeder 12 througha conduit 16 which opens into the upper end of the holder 46 above thedistributor 49.

Preferably, the base of the cone 11 is relieved to form a bottom surface54 spaced axially inwardly from the lower edge 18 to provide for aninternal conical surface 56 which intersects the conical outer surface10 so that the annular edge 18 is of maximum sharpness to increase theconcentration of electrical charge.

Referring now to FIG. 4, the discharge head 8 is shown in a differenttype of burner wherein the ring electrode is replaced by a screen 66 ofmetallic mesh supported on brackets 61 of electrically insulatingmaterial. The screen functions both to attract the oil particles fromthe adjacent edge 18 of the conical surface 10 and to stabilize theflame burning circumferentially around the screen of). In this case, ablower 22 assisted by an air deflector 63 is provided to agitate the airwithin the burner at low pressure intimately to mix the fuel and airabout the screen 60, and the screen acts as a flame barrier.

Any suitable furnace structure may be employed, but, for purposes ofillustration, there is shown an open top furnace 64 of any suitablematerial. The fuel line 16 is introduced through the wall of the furnacefrom which it is electrically insulated, as at 39, and is positioned tohold the electrostatic cone 11 at the desired elevation. The screen isof sufliciently large mesh to pass the oil droplets freely, and it ispossible to adjust the voltages and spacing between the screen 60 andthe annular edge 18 of the cone so that as the oil droplets approach thescreen opening, the charge thereon is reversed so that the wire in thescreen repels the droplets and prevents im pingement of them on the wireitself, while the momentum of the droplets helps to carry them throughthe screen and into the combustion zone.

Referring now to FIG. 5, the embodiment of the atomizer illustratedtherein comprises a discharge head 70 in which the film-forming surface72 is the upper face of a disk 74 of electrically conducting material.The peripheral edge 76 of the disk is made sharp to increase theconcentration of electrical charge there.

An element 78 of porous material, such, for example, as a poroussintered metal structure, is secured to the center of the disk, and theconduit 16 delivers the liquid fuel to be atomized to the element 7 S.

The porosity of the element 78 is chosen to permit the liquid fuel toflow through it and exit from around its entire circumference and on tothe surface 72 in regulated amounts in accordance with the quantity ofthe liquid fuel supplied through the conduit 16. A sintered bronze ofapproximately 25 to 50 micron porosity has been found satisfactory forthis purpose for use in atomizers of the capacity required for homeheating furnaces. The liquid issuing from the element 78 is spread overthe surface 72 in the form of a film.

A ring electrode 20 is positioned below and concentric with the disk 74.The discharge head 70 and electrode 20 are connected in an electricalcircuit in the manner indicated for the embodiment illustrated in FIG. 1and operate to atomize the liquid fuel through the operation of theelectrostatic field created between the disk 74 and the electrode 20 asdescribed heretofore.

It may be noted that for the purpose of this invention the physicalshape of the film-forming surface is not critical to the properfunctioning of the apparatus provided this surface produces film-likeamounts of liquid with sutflcient electrical charge to be drawn off froman edge of the surface in atomized form through the interaction of anelectrode adjacent to but spaced apart from this edge.

While this invention has been described in connection with preferredembodiments thereof, it is to be understood that the atomizing head andelectrode may be employed in various furnace arrangements and withvarious flame stabilizing means, and that other modifications andimprovements to the apparatus may be made without departing from theconcept of this invention, the scope of which is defined by the claims:appended hereto.

I claim:

1. An electrostatic atomizer for liquids comprising a discharge head fora liquid to be atomized, means for delivering said liquid to said head,an electrode positioned adjacent to and spaced apart from said head, anelectrical circuit including said head and said electrode as terminalelectrodes, a source of continuous direct current potential connected tosaid head to maintain said head at a continuous direct currentpotential, a source of alternating current potential connected to saidelectrode, the difference in potential between said head and saidelectrode cyclically varying an amount sufficient to cause said liquidto be drawn in atomized form from said head during alternate half cyclesof the alternating current potential of said electrode.

2. An electrostatic atomizer for liquids comprising a discharge head fora liquid to be atomized, said head formed with at least one thin edge ofelectrically conductive material, flow means for conducting said liquidto said head at said edge, an electrode disposed in adjacent parallelrelationship to and spaced apart from said edge, an electrical circuitincluding a source of continuous direct current potential connected tosaid head to maintain said edge continuously at a direct currentpotential and a source of alternating current potential connected tosaid electrode, the difference in potential between said edge and saidelectrode cyclically varying an amount sufficient to cause said liquidto be drawn in atomized form from said edge during alternate half cyclesof the alternating current potential of said electrode.

3. An electrostatic atomizer for liquids comprising a discharge headhaving a surface to receive a liquid film thereon and with said surfaceterminating in a substantially sharp peripheral edge of electricallyconducting material with said edge disposed in a plane, an electrodepositioned adjacent to said edge and disposed in a plane ,insubstantially parallel relationship to and spaced apart from the saidplane of said edge, means for depositing a film of liquid on saidsurface, means for conducting said liquid to said edge, and anelectrical circuit including said head and said electrode as terminalelectrodes and comprising a source of continuous direct currentpotential connected to said head and a source of alternating currentpotential connected to said electrode, the difference in potentialbetween said head and said electrode cyclically varying an amountsuificient to cause said liquid to be disengaged in atomized form fromsaid edge during alternate half cycles of the alternating currentpotential of said electrode.

said edge, an electrode in the form of a ring disposed in a plane inadjacent parallel relationship to the said plane of said edge and spacedapart from said edge, a source of direct current potential connected tosaid surface and maintaining said surface continuously at a directcurrent potential, a source of alternating current potential connectedto said ring, the difference in potential between said edge and saidring cyclically varying an amount sufficient to cause said liquid to bedrawn in atomized form from said edge during alternate half cycles ofthe alternating current potential of said electrode.

5. A11 electrostatic atomizer comprising a discharge head for a liquid,said discharge head having an external conical liquid flow surface ofelectrically conductive material and arranged with the axis of saidconical surface upright and said conical surface diverging downwardlyand terminating in a substantially sharp lower edge, liquid flow meansadapted to distribute a liquid around said conical surface above saidlower edge, said flow surface conducting said liquid to said edge, asource of direct current potential connected to said conical surface andmaintaining said surface continuously at a direct current potential, anelectrode in the form of a ring spaced adjacent to and below said loweredge with the axis of said ring in coaxial alignment with the said axisof said conical surface, a source of alternating current potentialconnected to said ring, the difference in potential between said edgeand said ring cyclically varying an amount sufiicient to cause saidliquid to be drawn in atomized form from said edge during alternate halfcycles of the alternating current potential of said ring,

6. An electrostatic atomizer comprising a discharge head including abase of electrically conductive material, said base having an externalconical surface arranged with the axis thereof upright and terminatingin a lower edge disposed in a horizontal plane at the maximum diameterof the cone, a holder for said base, said holder having an internalannular surface narrowly spaced from said external conical surface toprovide an annular flow port therebetween, means for supplying liquid tosaid flow port to flow over said conical surface and to said lower edge,a source of continuous direct current potential connected to said baseand maintaining said base continuously at a direct current potential, anelectrode in the form of a ring disposed in a horizontal plane spacedbelow and in parallel relationship to the said plane of said lower edgeand with said ring in coaxial relationship with the axis of said cone, asource of alternating current potential connected to said ring, thedifference in potential between said edge and said ring cyclicallyvarying an amount sufficient to cause said liquid to be drawn inatomized form from said edge during alternate half cycles of thealternating current potential of said ring.

7. A fuel burner comprising a furnace chamber, a discharge head for aliquid fuel in said furnace chamber, said discharge head having anexternal conical liquid flow surface terminating in a lower edge at themaximum diameter of said conical surface, means forming flow portsadapted to distribute a liquid fuel around said conical surface to flowto said lower edge, said flow surface being of electrically conductivematerial, conduit means for delivering liquid fuel to said flow ports, asource of direct current potential connected to said conical surface tomaintain said surface continuously at a direct current potential, anelectrode ring spaced below and adjacent to said lower edge, a source ofalternating current potential connected to said electrode ring, thepotential difference between said edge and said ring cyclically varyingan amount sufficient to cause said liquid to be drawn in atomized formfrom said edge during alternate half cycles of the alternating currentpotential of said ring, and means for directing a current of air throughsaid chamber.

8. A fuel burner comprising a furnace chamber having an atomizing zoneand a combustion zone, a discharge head for a liquid fuel in theatomizing zone of said furnace, said discharge head having anelectrically conductive external conical flow surface for said liquidfuel and arranged with its axis upright and terminating in a lower edgewith said lower edge disposed in a plane at the maximum diameter of thecone, means forming flow ports adapted to distribute said liquid fuelaround said conical surface to flow toward and onto said lower edge,conduit means for delivering liquid fuel to said flow ports, a source ofdirect current potential connected to said discharge head, an electrodering positioned in a plane disposed in spaced-apart parallelrelationship to the plane of said lower edge and with said ring incoaxial alignment with the axis of said conical surface, a source ofalternating current potential connected to said electrode ring, an airbloiwer communicating with said furnace chamber to direct a current ofair through said furnace chamber, flame stabilizing means separatingsaid atomizing zone and said combustion zone, the potential differencebetween said edge and said electrode ring cyclically varying an amountsufiicient to cause said liquid fuel to be disengaged in atomized formfrom said edge during alternate half cycles of the alternating currentpotential of said electrode ring.

9. A fuel burner comprising a furnace chamber having an atomization zoneand a combustion zone, a discharge head for a liquid fuel in saidatomization zone, said disge head formed with a substantially thindischarge edge, conduit means for delivering liquid fuel to said aaeaaaedischarge head to be discharged at said discharge edge, a source ofcontinuous direct current potential connected to said discharge head, anair blower directed to discharge air into said furnace chamber, ametallic screen of suitable mesh to pass fuel droplets placed adjacentto and spaced apart from said edge in parallel relationship therewithand separating said atomization and said combustion zones, a source ofalternating current potential connected to said screen, the potentialdifierence between said edge and said screen cyclically varying anamount sulncient to cause said fuel to be drawn from said edge inatomized form during alternate half cycles of the alternating currentpotential of said screen.

16. An electrostatic atomizer for liquids comprising a discharge head, ahorizontally disposed disk of electrically conductive material on saiddischarge head and having an upper surface formed thereon, said diskhaving a substantially sharp peripheral edge, said edge disposed in ahorizontal plane, means for conducting a liquid to said discharge head,means for distributing said liquid over the said upper surface of saiddisk to flow to said peripheral edge, an electrode in the form of a ringdisposed in a plane in adjacent parallel relationship to and spacedbelow the said plane of said peripheral edge and with the axis of saidring in alignment with the axis of said disk, a source of continuousdirect current potential connected to said disk, at source ofalternating current potential connected to said electrode, thedifference in potential between said edge and said ring cyclicallyvarying an amount suflicient to cause said liquid to be drawn inatomized form from said edge during alternate half cycles of thealternating current potential of the said ring.

References Cited by the Examiner UNITED STATES PATENTS 2,525,347 10/1950Gilman 3173 2,893,893 7/1959 Crouse 158-28 3,167,109 1/1965 Wobig l5828JAMES W. WESTHAVER, Primary Examiner.

7. A FUEL BURNER COMPRISING A FURNACE CHAMBER, A DISCHARGE HEAD FOR ALIQUID FUEL IN SAID FURNACE CHAMBER, SAID DISCHARGE HEAD HAVING ANEXTERNAL CONICAL LIQUID FLOW SURFACE TERMINATING IN A LOWER EDGE AT THEMAXIMUM DIAMETER OF SAID CONICAL SURFACE, MEANS FORMING FLOW PORTSADAPTED TO DISTRIBUTE A LIQUID FUEL AROUND SAID CONICAL SURFACE TO FLOWTO SAID LOWER EDGE, SAID FLOW SURFACE BEING OF ELECTRICALLY CONDUCTIVEMATERIAL, CONDUIT MEANS FOR DELIVERING LIQUID FUEL TO SAID FLOW PORTS, ASOURCE OF DIRECT CURRENT POTENTIAL CONNECTED TO SAID CONICAL SURFACE TOMAINTAIN SAID SURFACE CONTINUOUSLY AT A DIRECT CURRENT POTENTIAL, ANELECTRODE RING SPACED BELOW AND ADJACENT TO SAID LOWER EDGE, A SOURCE OFALTERNATING CURRENT POTENTIAL CONNECTED TO SAID ELECTRODE RING, THEPOTENTIAL DIFFERENCE BETWEEN SAID EDGE AND SAID RING CYCLICALLY VARYINGAN AMOUNT SUFFICIENT TO CAUSE SAID LIQUID TO BE DRAWN IN ATOMIZED FORMFROM SAID EDGE DURING ALTERNATE HALF CYCLES OF THE ALTERNATING CURRENTPOTENTIAL OF SAID RING, AND MEANS FOR DIRECTING A CURRENT OF AIR THROUGHSAID CHAMBER.